ISSN:
0142-2421
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Physics
Notes:
Oxidized beryllium surfaces are used in a number of microwave crossed-field amplifier (CFA) tubes as secondary electron emission cold cathodes. During operation the cathode surface is subjected to electron and ion bombardment in a complex process which produces both erosion and replenishment of the oxide surface, in addition to a significant build-up of amorphous carbon. The result is a general degradation of tube performance. Special techniques were developed to opoen an evacuated tub and transfer the cathode to a UHV surface analysis system with minimal contamination from the atmosphere. Three CFA tubes with various histories of operation were examined and measurements from made of the secondary electron emission (delta), first crossover, voltage at delta maximum, and the surface chemical composition by AES at several points on each cathode. Significant differences were found which reflected their number of hour of operation, as well as variations in manufacturing procedures. A generalized linear cofrrelation between secondary electron emission and the surface carbon atomic fraction was obtained when the data for all the tubes was combined and analyzed. The deleterious effects of carbon in operated CFA tubes were confirmed and suggest that reduction of potential sources of carbon contamination in the tube during manufacture, processing, and operation should improve overall performance.
Additional Material:
16 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/sia.740110620
